Phase Ii Trial Of Pembrolizumab (Pem) Plus Granulocyte Macrophage Colony Stimulating Factor (Gm-Csf) In Advanced Biliary Cancers (Abc).

386Background: The efficacy of immune checkpoint inhibition (CPI) has not been established in ABC. GM-CSF modulates immune effector cells and has demonstrated safety and improved survival (OS) in combination with ipilimumab in melanoma. This phase 2 trial aims to evaluate the efficacy and safety of PEM in combination with GM-CSF in ABC. Methods: Design: Simon’s 2-stage. Key eligibility: ABC with progression/intolerance on ≥ 1 standard therapy, no prior CPI, bilirubin ≤1.5xULN. Treatment: PEM 200 mg IV Q21 days plus 2 cycles of GM-CSF 250 µg SC D1-14 Q21 days in cycles 2 and 3 (Stage 1 Safety Cohort) or in cycles 1 and 2 (Stage 2). Endpoints: 1◦: Progression-free survival at 6 months (PFS6) with H0 25% vs. H1 50%. Key 2◦: Safety, overall response rate (ORR) and duration (DOR), OS, PD-L1 expression. Exploratory: PBMC and tumor immune cell profiles, tumor genotype, microsatellite (in)stability (MSI or MSS). Results: Accrual has completed with 27 patients (pts) enrolled 5/2016-6/2017: F/M 13/14; median age 61...